The objective of this project is to test the hypothesis that exercise has both inbibitory and excitatory effects on food intake at different times after the exercise has terminated, and that these effects differ across degree of overweight and between sexes. The health related importance of this work is that exercise is frequently prescribed as an adjunct to other weight loss regimens without adequate evidence of its effects on food intake. One barrier to the study of the effect of exercise on food intake is that no short term paradigm exists. Previous studies of the effect of exercise on food intake have been labor-intensive, time consuming, and prolonged. The paradigm to be used in the present study is much shorter and allows the testing of more subjects in the same time. Subjects exercise on a bicycle ergometer and then eat a test meal in a well controlled situation using a computerized eating monitor. The exercise-food intake paradigm has been validated by showing that strenuous exercise will inhibit food intake in non-obese women, as has been shown previously in some animal studies. In the present proposal four questions about the relationship between exercise and food intake will be addressed: 1) Does the inhibitory effect of exercise on food intake persist or reverse to an excitatory effect after several hours. 2) Does the effect of exercise on food intake differ between obese and non-obese persons and between men and women? 3) Does exercise have a graded or an all or none effect on food intake? 4) Does the perception of differing amounts of exertion effect food intake when actual energy expended by subjects is held constant? These questions will be answered by varying the types of human volunteers studied, the amount of exercise given, the time interval from exercise to eating, and the type of exercise. It is hoped that the results will be applicable to the specification of programs to inhibit food intake and thereby result in weight loss, and that the methods will facilitate study of the mechanism by which energy expenditure is related to energy intake.